Problem: Let $f(x) = 10x^{2}+5x-7$. Where does this function intersect the x-axis (i.e. what are the roots or zeroes of $f(x)$ )?
Answer: The function intersects the x-axis when $f(x) = 0$ , so you need to solve the equation: $10x^{2}+5x-7 = 0$ Use the quadratic formula to solve $ax^2 + bx + c = 0$ $x = \dfrac{-b \pm \sqrt{b^2 - 4ac}}{2a}$ $a = 10, b = 5, c = -7$ $ x = \dfrac{-5 \pm \sqrt{5^{2} - 4 \cdot 10 \cdot -7}}{2 \cdot 10}$ $ x = \dfrac{-5 \pm \sqrt{305}}{20}$ $ x = \dfrac{-5 \pm \sqrt{305}}{20}$ $x =\dfrac{-5 \pm \sqrt{305}}{20}$